1. Technical Field
The present invention relates to a light source device and a projector.
2. Related Art
In many cases, a light source device of a projector is constituted by a discharge light emission type light source device which induces discharges between a pair of electrodes for light emission.
More specifically, this type of light source device includes an arc tube which has a substantially spherical light emission portion containing a discharge space inside, and a pair of sealing portions extending in directions away from each other from both ends of the light emission portion. During lighting of the arc tube, the upper part of the light emission portion has the highest temperature, and the lower part of the light emission portion has the lowest temperature.
When this high-temperature condition of the upper part of the light emission portion continues, the transparency of the light emission portion easily decreases. Moreover, when the temperature difference between the upper part and the lower part increases, blacking of the light emission portion easily occurs. For avoiding these problems, the upper part of the light emission portion needs to be efficiently cooled.
As a technology capable of meeting this requirement, a projector which supplies cooling air to the upper part of the light emission portion to efficiently cool the upper part of the light emission portion has been proposed (for example, see JP-A-2006-91132).
According to the projector (projection apparatus) disclosed in JP-A-2006-91132, a channel of cooling air provided on the projector is controlled by a rotational member (cooling air guide plate) such that cooling air can be supplied to the upper part of the light emission portion (upper surface of discharge lamp) in either the normal position (normal installation) or the suspended position (suspended installation) of the projector.
JP-A-2006-91132 also discloses a structure which controls the channel of cooling air such that cooling air can be supplied to the upper part of the light emission portion in either the normal position or the suspended position of the projector by rotation of the rotational member rotatable by gravity (see JP-A-2006-91132, FIG. 3 and others).
According to the structure which rotates the rotational member by gravity, however, the channel of cooling air is insufficiently controlled when the rotational member is too small to obtain enough gravity torque for rotation. In this case, the upper part of the light emission portion is not efficiently cooled, which leads to deterioration of the arc tube and prevents elongation of the life of the arc tube.
As a method for overcoming these drawbacks, there is an idea that the rotational member is rotated by a force other than gravity (for example, see JP-A-2006-91132, FIGS. 6 and 8 and others). In this case, however, another mechanism which controls the channel of cooling air (control mechanism using a spring or the like) needs to be added to the rotational member, which increases the size of the light source device.